Two people in games like Halo or Call of Duty that will almost always be seen together in attempt to outnumber any opponent that would attempt a one on one encounter. Usually wont get any kills without their ass pal right next to them to weaken or finish their enemy.
So close that their usually on each others ass getting kills.
"I would have got him if his Ass Pal wasn't right there."
"Wheres my team I cant take these Ass Pals alone"